Roadable aircraft present many design challenges. For example, the craft must be small enough in its retracted or folded position to fit within (standard) garages, drive-up facilities and parking facilities, which limits the principle dimensions to a volume of 20 feet by 7 feet by 7 feet. In order to fit within the current transportation system to avoid heavy glass and all wheel braking, the craft should be below 1500-pound empty weight (curb weight) and licensed as a 3-wheeled motorcycle.
The folding and storing of the wings presents particular difficulty. If the wings are folded aft, the aircraft may fall on its tail. If the wings are folded forward to a preferred center of gravity (CG) location, then the wing may block the visibility of the operator. If the wing is stored on top of the vehicle, gusts from passing trucks may blow the vehicle over on the ground. Detachable wings have been tried in past, for example, the Molt Taylor Aerocar. However re-attaching the wings in less than perfect weather conditions provides difficulty even for trained personnel. Some Prior Art Roadable aircraft, such as the Aerocar, towed the wing and tail along in trailer fashion, which created additional problems, such as clearance and susceptibility to cross-winds on the road. Damage to the control surfaces on the ground must be minimized so the wing needs to be stored where it can be protected. Complex folding mechanisms are prone to failure, require maintenance, and are heavy. Wings and flying surfaces dangling off the aircraft provide poor aesthetics for the vehicle.
In order to move the aircraft on the ground several schemes have been employed. A common method is to provide a clutch to the main engine and power is sent through a heavy transmission. Some designs use hydraulic motors in the main gear driven by a hydraulic pump off the main engine. Others use a totally separate engine for roadable power. There are many ways others have dealt with the problem of operational controls of roadable aircraft and flying cars. The principle problem is that there is a mix between the roll and yaw axis in the separate vehicles.
Another problem is in the layout of road and flying controls. One designer placed the flight controls in the left side of the cockpit and the ground controls on the right. Another designer placed the controls up under the panel where the operator pulls them out when usage is desired. Another designer has the control wheel designed such that the wheel is in half and then it is rotated upward to form a complete circle for road use. Another designer suggests using a steering wheel oriented such that it resembles ones used in buses to overcome this obstacle. Other have the controls located outside or mixed between existing controls, causing possible confusion in emergency situations. Each of these Prior Art designs has their advantages and disadvantages. A simple lightweight solution is needed to meet each of these needs. Yet provides enough difference from one vehicle to the other so that the operator identifies which vehicle he is operating even in emergency situation
More than 70 auto-planes have been designed and patented over recent decades but all seem to have complex structures which are incapable of quick and convenient conversion from plane to road vehicle and vice versa. Williamson, U.S. Pat. No. 4,358,072, incorporated herein by reference, describes a land vehicle and aircraft combination, which has separate engines for the land vehicle and the aircraft. This particular Prior Art invention involves a land vehicle, which physically separates from an aircraft fuselage. While this allows a pilot to “fly” his auto, it requires complicated folding stock for aircraft controls, fuselage tilting or jacking, airport storage area for the fuselage which must be left behind and return to the point of landing for further flying.
Miller, U.S. Pat. No. 4,269,374, incorporated herein by reference, is directed to an auto-plane which has wing and tail structures that are movable outwardly for flying and inwardly for storage and road vehicle use. All of the parts remain intact in both the road and the flying forms. However, the Miller device has complicated fold away wheels and has wings that fold away in a complicated and complex fashion, namely, the front wings must be rotated about a fixed line 90 degrees from horizontal surface to vertical surface, and also be swung into the side of the vehicle 90 degrees, and must be folded in half along their lengths, requiring rotatability, lengthwise foldability and upward swivelability. The Miller design also has a tailpiece and tail wing that must not only slide forward but also downward. This Prior Art auto-plane is very complex and, while it embodies the basics of wing hingeability, locking pins and folding mechanisms, it illustrates vividly what an auto-plane should not be if it is to be convenient, practical, cost effective, and safe.
Groeger, U.S. Pat. No. 4,165,846, incorporated herein by reference, teaches a land-air-water vehicle having doors which open to become wings, and a large diameter set of tires which acts to assist in both land and water propulsion. Unwindable fins are used for control. Millman, U.S. Pat. No. 3,614,024, incorporated herein by reference, describes a combined watercraft and aircraft having folding wings so that the aircraft can rest on a remotely controlled watercraft. The watercraft is controlled by the pilot as a tow means until flying velocity and altitude are achieved, at which time the tow rope is “unreeled” and the aircraft is flown as a glider.
Strong, U.S. Pat. No. 3,612,440, incorporated herein by reference, illustrates a warp action spoiler plate aileron in a combined airplane and automobile. This Prior Art auto-plane has wings which swing 90 degrees back into the body of the vehicle. Unfortunately, the folded wings must overlap one another in their storage slot and so must move up or down as they are swung in so as to render one partially over the other. Schertz, U.S. Pat. No. 3,371,886, incorporated herein by reference, teaches an auto-plane wherein each wing is twice hinged and the outer portion folds 180 degrees over and flat with an inner portion, and then both the inner and outer portions as a single entity are folded upwardly 90 degrees against one of two vertical stabilizers (twin tails). Unfortunately, these twice folded stored vertical wing portions render the auto-plane very top heavy. Further, they create the need for significantly more hardware, hinges, locking mechanisms, and create a four-wing thick top clearance problem.
Zuck, U.S. Pat. No. 3,138,351, incorporated herein by reference, describes an auto-plane wherein the wings swing back up so as to partially rest upon one another. Not only are complex wing movements required, but also the wing support struts are cut and hinged so as to break and swing inwardly in an awkward and broken path. Zuck requires substantial, complex fold up hardware typical of the prior art. Mills, U.S. Pat. No. 3,065,927, incorporated herein by reference, illustrates an auto-plane with a top propeller (single prop gyrocopter) and wings which fold in. Each wing has two break points and two sets of hinges, again requiring more hardware and weight.
Bland, U.S. Pat. No. 2,940,688, incorporated herein by reference, discloses an aircraft adaptable for road vehicle use and for sailing as a sailboat. The wings rotate 90 degrees up and are secured to the roof when the invention is used as a sailboat. When used as a road vehicle the wings rotate 90 degrees up and then twist 90 degrees to overlap one another and then drop back 90 degrees to lay atop the vehicle. The tail has dual rudders and elevators, one of each on a telescoping tubular member. Unfortunately, storage of the wings for road use requires a complex. series of three different motions and the necessary hardware, hinges and latches to achieve these. Bland teaches a retractable tail but the method of operation is external to the telescopic tubes and individually operated.
Perel, U.S. Pat. No. 2,573,271, incorporated herein by reference, discloses a method to pivot two wings into a fuselage for storage. This method leaves the delicate control surfaces in a position which is likely to be damaged. Pham, U.S. Pat. No. 6,129,306, incorporated herein by reference, discloses a wing that is rotatably mounted on top of a fuselage on a wing pivot mechanism whereby the wing is horizontally rotatable between a flight position with the wing span approximately orthogonal to the fuselage's longitudinal axis and a roadable position with the wing span approximately parallel to the longitudinal axis of the fuselage, thereby allowing the vehicle to have a maximum width within legal limit for use in the roadway.
Wooley, U.S. Pat. No. 6,224,012, incorporated herein by reference, discloses a wing positioned above a fuselage of a vehicle with means to rotate the wing a nominal ninety degrees about a vertical axis from a flight position to a ground travel position where the wing span is aligned with the fuselage. Einstein, U.S. Pat. No. 4,627,585, incorporated herein by reference, discloses a Telescopic tail section but fails to teach a method of deployment and method to synchronize its movements in order to prevent binding. In the absence of a synchronizing method one side even slightly out of alignment due to wear or manufacturing tolerances will bind and not function properly.
McCoskey, Published U.S. Patent Application No. US2006/0065779, incorporated herein by reference, discloses using electrical power to move an aircraft on the ground using only the nose wheel. The motor is not integrated into the wheel and contains planetary gears systems and a cone clutching devise. Further the stator and rotor are not optimized for maximum torque. Because the motor is not integrated into the wheel it provides a drag configuration especially for fixed wing aircraft.